1. Field of the Invention
The present invention relates in general to audiovisual slide projectors and more specifically to the muting of the audio output of such projectors during each slide change cycle.
2. Description of the Prior Art
The broad concept of the use of a muting circuit in magnetic playback or recording equipment is old as illustrated by U.S. Pats. to Ban, No. 3,673,345, and Tsuji, No. 3,705,272. The Ban patent discloses a muting circuit that acts on the output amplifier circuit of a magnetic tape player to disable the power therefrom when the player is switched from a normal to a fast tape drive condition. The Tsuji patent teaches a muting circuit coupled to a high frequency biased record-reproduce system to interrupt the high frequency biasing signal during the interval while the system is being switched from a record mode to a reproduce mode. In this way, noise is eliminated that normally would be present as a side effect of the high frequency biasing signal.
Both of the above described muting circuits achieve the goal of eliminating noise from magnetic record-reproduce devices. However, both systems add to the complexity of the devices on which they are employed since they include switching apparatus that would otherwise not be needed. The present invention provides a muting circuit that is relatively simplistic in nature and as such adds no switching apparatus to the basic circuitry of the device on which it is employed.